The White House mess -- the military-inspired term for the West Wing cafeteria -- opens at 7 a.m. each day. And each day, there is a long line of hungry staffers who have already been at the office for well over an hour.

By 8 p.m., as the doors to the mess are about to close, the orders flow again as bleary-eyed staffers grab dinner before heading back to their offices for another conference call or meeting.

"I think the mess hates all of us," said a frequent customer who is a senior adviser to President Obama.

In a city where work can border on obsession, the Obama staffers stand out. They are not quite the walking dead, but their eyes are frequently ringed with the bags that accompany exhaustion.

"This is a place, because of the stress, the schedule and the sheer hours, that just chews people up and spits them out," said press secretary Robert Gibbs, whose alarm clock is set to 4:30 a.m., though he ignores the early ring more often these days.

All West Wings face fatigue at some point, but the Obama team has had a particularly frenetic start, the result of inheriting the worse economic crisis since the Great Depression and the team's own seemingly chaotic drive to push an agenda that includes the creation of a new health insurance system, auto bailouts, Middle East peace, nuclear nonproliferation, two wars and education reform.

Political Washington has long fostered a workaholic culture, the expectation that the rewards of service on the big stage of national government come with 18-hour, on-call days. But even the most hardy of Obama's staff members are beginning to recognize the toll that the pace is taking.

"I felt like a heavyweight boxer lying on the mat," Gibbs said last week, describing his mood before leaving with the president for an eight-day trip across 10 time zones.

Air Force One landed early yesterday at Andrews Air Force Base, carrying a presidential team that caught just a few hours of sleep each night in Russia, Italy and Ghana. All plan to return to work before sunrise today.

The grueling schedule has forced most of the presidential aides to abandon physical exercise, and the few who persist -- often because of incessant goading from their fitness-fixated commander in chief -- have planned their workouts at times that stretch their schedules even further.

Chief of Staff Rahm Emanuel arrives at the House of Representatives gym at 5:30 a.m.; his top aide, Sarah Feinberg, starts her workout at a Water Street gym at 5:15 a.m. By 5:30 a.m., the White House Bulletin -- a compilation of political clippings from newspapers and Web sites -- appears in inboxes and on BlackBerrys, demanding attention. By 7 a.m., West Executive Drive between the White House and the Eisenhower Executive Office Building is filled with staffers' cars.

Obama's top aides gather in Emanuel's office at 7:30 a.m. daily. Gibbs -- like his predecessor, Dana Perino -- arrives not long after 6 a.m. to get ready for the meeting.

"What was striking about the 24/7 was the 7," said Gene Sperling, a counselor to Treasury Secretary Timothy F. Geithner and a veteran of the Clinton White House. "Between every financial crisis response, autos, recovery -- weekends could be a nonstop conference call. Thankfully, it's gotten a bit better."

Members of President George W. Bush's White House recall similar 18- and 20-hour workdays, especially in the aftermath of the Sept. 11, 2001, attacks and during the early stages of the war in Iraq. And Bill Clinton's staffers -- many of whom have returned to the White House after eight years -- were no strangers to sleepless nights as the 42nd president set a frenetic pace throughout his administration.

"There's the pace. There's the hours. There's the intensity. There's the anxiety. There's the pressure for results," said Perino, Bush's last press secretary, who worked in the White House for about seven years. "I used to get up at 4 a.m. every day. It was like being shot out of a cannon."

It has only been six months for Obama's team, but almost all of the president's top and mid-level aides took their posts straight out of the longest presidential campaign in history.

Obama is now testing the limits of his staffers' endurance. So far, there is a palpable sense of pride in the West Wing that treaties are negotiated, complex legislation is crafted and banks are bailed out -- all on very little sleep.

"We stay late every night, work weekends -- basically on 24/7," Mike Hammer, a spokesman for the National Security Council, wrote in an e-mail while on a recent trip abroad. "Not sure what example to give you but here I am at 12:30 am in Islamabad with General [James L.] Jones and answering your email," he wrote, referring to the national security adviser.

During the first two months of the administration, White House and Treasury officials tried to deal with the worsening economy almost without a break. The image of senior economic adviser Lawrence H. Summers nodding off during a presidential meeting with credit card executives became the emblem of that period.

Behind the scenes, it was even worse. The night before Obama announced the administration's housing plan on Feb. 18 in Arizona, Sperling e-mailed the final documents at 3 a.m. and asked for comments. Five people responded immediately.

Martin Moore-Ede, a former Harvard University professor, calls it the "iron man" syndrome and says the American political workplace is one of the few that still resists a mechanism for ensuring people get rest.

One study conducted for the British Parliament found that "mental fatigue affects cognitive performance, leading to errors of judgement, microsleeps (lasting for seconds or minutes), mood swings and poor motivation." The effect, it found, is equal to a blood alcohol level of .10 percent -- above the legal limit to drive in the United States.

Obama administration officials, and their predecessors, shrug off such warnings, citing the adrenaline rush. They insist that their bodies have grown strangely accustomed to the rhythms of the job. But they acknowledge that the routine in the White House is more grueling than most had anticipated.

The staff is beginning to take a few breaks. One deputy press secretary found time to get away to Hawaii for a few days. Gibbs went to his high school reunion in Alabama, the first weekend away that he can remember.

But, he says, it is not enough.

"You go down to the mess. You have your coffee at five in the afternoon, and it just doesn't do anything," Gibbs lamented. "Because you realize you're so far behind [in sleep] that a jolt -- you don't even feel it."